This invention relates to a breathing apparatus and more particularly to a self-contained portable breathing apparatus for temporary use by a wearer in a noxious atmosphere, such as is worn by fire fighters when exposed to smoke or noxious gases.
Such portable breathing apparatuses are generally either of the open loop or the closed loop type. In the open loop system, compressed air is delivered to the wearer and the expired gases are vented to the atmosphere. Such systems are relatively simple and have the advantage of providing cool breathing gas and a minimum of breathing resistance. However, since the gas is not reused, a system of reasonable weight has a relatively short duration of breathing supply, while being relatively heavy. In a closed loop system, the exhaled gases are directed through a device that generates oxygen or at least removes the carbon dioxide from the gas, which is recycled to the wearer, and although some high pressure gas is normally supplied, the gas tank is relatively small and lightweight, so that the breathing system provides a relatively long duration of air supply while being relatively lightweight. However, such systems have the disadvantage of a relatively high breathing resistance, a moisture buildup in the system, and a heat buildup in the recycled gas, so that the wearer is breathing relatively warm gas.
Typically, prior systems have featured a face mask that is uncomfortable and cumbersome for the wearer, and while some of the more modern systems have utilized a helmet, it has still been necessary to provide a face seal with its attendant disadvantages.